Heretofore in shiftable mechanisms and particularily control valves which require alternate actuation between two positions, there has been necessitated electrical operated pilot valves and related pressure sensing equipment for shifting the spool of a valve between two extreme positions. This was for controlling the flow of pressure fluids, for example, from an inlet port to one of a pair of cylinder or outlet ports. The use of electrical operated pilot valves increased manufacturing costs as well as maintenance problems.
Heretofore in employing electrically operated pilot valves operating a shiftable mechanisim such as a valve spool between one of a pair of positions of control, such electrical control mechanisms had to be of such size as to be effective in controlling reciprocal movements of the shiftable spool or valve element.
Increased space was needed and a considerable number of additional parts were required to be stocked for the assembly of such electrically operated pilot valves.